An investigation into why an RAF Hercules crashed into the Iraqi desert killing all ten people on board could take weeks, it emerged today.

The marshy terrain and hostile local forces are likely to hamper the painstaking hunt for clues, a Ministry of Defence spokesman said. He described as "speculation" press reports that they were considering the possibility a bomb may have been on board.

Nine RAF personnel and one soldier died in Sunday's crash, 25 miles north-west of Baghdad. The MoD today refused to comment on reports that the soldier was an Army NCO attached to the SAS.

Chief of the Air Staff Air Chief Marshal Sir Jock Stirrup announced that a senior investigator was on his way to Iraq, where staff have already been on the ground sifting through the wreckage. The MoD spokesman said of the probe: "It could take weeks."

Prime Minister Tony Blair said today it was still not clear how the crash happened.

An Iraqi militant group, Ansar al-Aslam, claimed on a website that it shot down the aircraft using an anti-tank missile. A second group of insurgents sent a video to Arabic TV channel al-Jazeera which claimed to show evidence that they brought down the plane.

The only victim to be named so far is Flt Lt Paul Pardoel, 35, an Australian. The father-of-three, originally from Victoria, previously served in the Royal Australian Air Force before joining the RAF. His father, John, said he was living in England with his wife Kellie, and children Jordan, seven, Jackson, five, and India, two.

* A BILL that would require the Prime Minister to seek MPs' approval before sending British troops to war was being published today.